It may be true that you can't judge a package by its cover, but when was the last time you enthusiastically opened a cheap, unattractive package...let alone a letter? You've worked hard to create professional printed marketing material and crafted just the right message. Make sure your reader sees it. Don't skimp on the envelope! With full color envelope printing from Seven Lines, stand out from the rest with brilliant, full color envelopes featuring your corporate logo and address. Full color printing on Regular and Window No. 10 envelopes. A No. 10 is the standard size envelope for business letterhead and stationery. The dimensions of No. 10 envelopes are 4 1/8" x 9 1/2".